Resin composition with a vinyl alicyclic hydrocarbon polymer

ABSTRACT

A resin composition comprising a vinyl alicyclic hydrocarbon polymer and a hindered amine light-resistance stabilizer having a number average molecular weight (Mn) of 1,000 to 10,000 and having excellent processing stability, light-resistance stability, heat resistance and transparency, and a light guide plate obtained by forming or molding the resin composition.

TECHNICAL FIELD

The present invention relates to a resin composition containing a vinylalicyclic hydrocarbon polymer, and more particularly to a resincomposition excellent in processing stability, light-resistancestability, heat resistance, transparency, etc. and suitable for use in aforming or molding material for light guide plates for back light inliquid crystal display devices. The present invention also relates tolight guide plates for plane emission illuminator, obtained by formingor molding said resin composition and used in back lights or frontlights in liquid crystal display devices.

BACKGROUND ART

A vinyl alicyclic hydrocarbon polymer is prepared by hydrogenating anaromatic ring of a vinyl aromatic polymer, for example, polystyrene. Thevinyl alicyclic hydrocarbon polymer is excellent in heat resistance,transparency, low water absorption property, etc. and is hence proposedto be used as a forming or molding material for optical disk substrates.The vinyl alicyclic hydrocarbon polymer is also excellent in chemicalresistance, low dissolution property, etc. and is hence proposed to beused as a forming or molding material for medical containers (JapanesePatent Application Laid-Open No. 6-199950).

As described above, the uses of the vinyl alicyclic hydrocarbon polymerare about to be spread. In order to more develop the uses thereof,however, it is necessary to improve it in such a manner that varioushigh properties required of each use can be exhibited while retainingits characteristic excellent properties such as high heat resistance andtransparency, and low water absorption property.

Examples of new uses of the vinyl alicyclic hydrocarbon polymer includea light guide plate for a plane emission illuminator used in a backlight or front light in a liquid crystal display device (LCD). In recentyears, LCDs have been spread as display devices in computers or carnavigation systems. The display by LCD is inconvenience in use at a darkplace because the LCD itself is non-luminous. Thus, a plane emissionilluminator uniformly illuminating a display part of the LCD has beendeveloped for the purpose of permitting improvement in ease of seeingand use at the dark place. In a light transmission type LCD, a backlight type that illumination is performed from a back side of a displaysurface is used, while a front light type that illumination is performedfrom a front side of a display surface is used in a light reflectiontype LCD.

Plane emission illuminators are roughly divided into an edge system anda vertical system according to the arrangement of a light source to thedisplay surface. In the back light type, either the edge system or thevertical system is selected as necessary for the end applicationintended. In the case of the front type, the edge system is used.

FIG. 1 illustrates a cross-sectional view of an exemplary back light ofthe edge system. A reflection layer 2 for diffusely reflecting light isprovided on a back surface of a transparent light guide plate 1. Thelight from a light source 4 (for example, cold cathode-ray tube)arranged at a side surface of the light guide plate 1 is diffuselyreflected or scattered by the reflection layer 2 and collected on theside (upper side in the drawing) of a liquid crystal display panel. Adiffusion plate 3 is arranged on the surface of the light guide plate 1on the side of the liquid crystal display panel as needed. Further, acondenser plate (not illustrated) may be arranged thereon. A reflectionplate may be arranged under the reflection layer 2 as needed.

The light guide plate is formed from a transparent synthetic resin suchas an acrylic resin for weight saving. As the reflection layer, an inkpattern may be formed on the reflection surface of the light guide plateby printing. Besides, there are reflection layers of various types, suchas those obtained by matting the reflection surface of the light guideplate, converting it into a Fresnel mirror or vapor-depositing aluminumthereon. The plane emission illuminator of the edge system may be madethin in thickness or large in size.

The light guide plate for the plane emission illuminator is required tohave a high available efficiency of light from a light source (lamp),thereby permitting high luminance, deteriorate physical propertiesthereof by heat generated from the lamp and have excellentlight-resistance stability.

As described above, the vinyl alicyclic hydrocarbon polymer is excellentin heat resistance, transparency, low water absorption property, etc.and hence attracts attention as a forming or molding material for lightguide plates for the plane emission illuminators. However, a light guideplate formed with the vinyl alicyclic hydrocarbon polymer involvesproblems that it is colored by long-term use, and gases of a volatilecomponent or the like are generated to cloud a cold cathode-ray tube(lamp) or a lamp reflector covering the cold cathode-ray tube.Therefore, the vinyl alicyclic hydrocarbon polymer does not fullysatisfy high properties required of the use as the forming or moldingmaterial for the light guide plates for the plane emission illuminators.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a resin compositionwhich contains a vinyl alicyclic hydrocarbon polymer and is excellent inprocessing stability, light-resistance stability, heat resistance,transparency, etc. and suitable for use as, for example, a forming ormolding material for light guide plates for plane emission illuminatorsin liquid crystal display devices.

Another object of the present invention is to provide a light guideplate for a plane emission illuminator in a liquid crystal displaydevice, obtained by forming or molding the resin composition havingexcellent various properties as described above.

The present inventors having carried out an extensive investigation witha view toward achieving the above objects. As a result, it has beenfound that the above objects can be achieved by a resin compositionobtained by incorporating a hindered amine light-resistance stabilizerhaving a molecular weight within a specified range in a specified amountinto a vinyl alicyclic hydrocarbon polymer.

The resin composition according to the present invention is excellent inheat resistance, transparency, light-resistance stability, processingstability, etc. Therefore, a light guide plate for a plane emissionilluminator formed with the resin composition according to the presentinvention not only has high initial luminance, but also is not coloredeven when it is used for a long period of time under lighting of a lampand causes neither the lamp nor a lamp reflector to be clouded bygeneration of gases. The present invention has been led to completion onthe basis of these findings.

According to the present invention, there is thus provided a resincomposition comprising a vinyl alicyclic hydrocarbon polymer and 0.01 to20 parts by weight, per 100 parts, by weight of the vinyl alicyclichydrocarbon polymer, of a hindered amine light-resistance stabilizerhaving a number average molecular weight of 1,000 to 10,000 asdetermined by gel permeation chromatography.

According to the present invention, there is also provided a light guideplate for a plane emission illuminator, obtained by forming or moldingsaid resin composition

BRIEF DESCRIPTION OF DRAWING

FIG. 1 is a cross-sectional view of an exemplary back light of an edgesystem in a liquid crystal display device.

BEST MODE FOR CARRYING OUT THE INVENTION 1. Vinyl Alicyclic HydrocarbonPolymer

The vinyl alicyclic hydrocarbon polymer used in the present invention isa polymer having repeating units of a structure that an alicyclichydrocarbon compound (hereinafter abbreviated as “vinyl alicyclichydrocarbon compound”) having a vinyl group has been subjected tovinyl-addition polymerization.

The vinyl alicyclic hydrocarbon polymer can be prepared by subjecting,for example, a vinyl alicyclic hydrocarbon compound such as avinylcycloalkene or vinylcycloalkane, or a monomer mixture containing avinyl alicyclic hydrocarbon compound and a monomer copolymerizable withthe vinyl alicyclic hydrocarbon compound to vinyl-additionpolymerization and then hydrogenating unsaturated bonds within alicyclicrings in the resulting polymer as needed.

The vinyl alicyclic hydrocarbon polymer can also be prepared bysubjecting an aromatic hydrocarbon compound (hereinafter abbreviated as“vinyl aromatic compound”) having a vinyl group, or a monomer mixturecontaining a vinyl aromatic compound and a monomer copolymerizable withthe vinyl aromatic compound to vinyl-addition polymerization and thenhydrogenating unsaturated bonds within aromatic rings in the resultingpolymer as needed.

The vinyl alicyclic hydrocarbon polymer is a homopolymer or copolymercontaining, in its main chain, repeating units [1] of a structurerepresented by the following formula (1):

wherein X is an alicyclic hydrocarbon group, and R¹ to R³ are,independently of one another, a hydrogen atom, linear hydrocarbon group,halogen atom, alkoxy group, hydroxyl group, ester group, cyano group,amide group, imide group, silyl group, or linear hydrocarbon groupsubstituted by a polar group.

In the case of the copolymer, it may be any of a random copolymer,pseudo-random copolymer, graft copolymer and block copolymer. Thestereoregularity of the chains of the repeating units [1] may be any ofisotactic, syndiotactic and atactic.

In the formula (1), X represents an alicyclic hydrocarbon group. Thenumber of carbon atoms forming the ring of this-alicyclic hydrocarbongroup is generally 4 to 20, preferably 5 to 7, more preferably 6 fromthe viewpoint of low birefringence, mechanical strength, etc.

The alicyclic hydrocarbon group is generally a saturated alicyclichydrocarbon group. However, carbon-carbon unsaturated bonds may becontained in a low proportion. The content of the carbon-carbonunsaturated bonds is at most 20%, preferably at most 10%, morepreferably at most 5% based on the whole carbon-carbon bond from theviewpoints of low birefringence, heat resistance, transparency, etc. Thecontent of the carbon-carbon unsaturated bonds can be determined by¹H-NMR measurement.

In the alicyclic hydrocarbon group, a part of hydrogen atoms bonded tocarbon atoms forming the ring may be substituted by any of hydrocarbongroups, polar groups and linear hydrocarbon groups substituted by apolar group. Examples of the polar groups include halogen atoms, alkoxygroups, a hydroxyl group, ester group, a cyano group, an amide group, animide group and a silyl group. An alicyclic hydrocarbon groupsubstituted by a linear hydrocarbon group having 1 to 6 carbon atoms ispreferred from the viewpoint of heat resistance, etc.

R¹ to R³ are preferably all hydrogen atoms or linear hydrocarbon groupshaving 1 to 20 carbon atoms (preferably 1 to 6 carbon atoms) from theviewpoint of heat resistance, low birefringence, mechanical strength,etc. The linear hydrocarbon groups may be substituted by a polar group.Examples of the polar group include halogen atoms, alkoxy groups, ahydroxyl group, ester group, a cyano group, an amide group, an imidegroup and a silyl group. Examples of the linear hydrocarbon groupsinclude alkyl groups and alkenyl groups. Among these, the alkyl groupsare preferred. The alkyl groups are preferably alkyl groups having 1 to20 carbon atoms (preferably 1 to 6 carbon atoms).

The content of the repeating units [1] in the vinyl alicyclichydrocarbon polymer is generally at least 50% by weight, preferably atleast 70% by weight, more preferably at least 80% by weight, mostpreferably at least 90%, by weight from the viewpoints of heatresistance, low birefringence and mechanical strength.

The repeating unit [1] is preferably a repeating unit [2] represented bythe following formula (2):

wherein R¹ to R³ are, independently of one another, a hydrogen atom oran alkyl group having 1 to 20 carbon atoms, and R⁴ to R¹⁴ are,independently of one another, a hydrogen atom, an alkyl group having 1to 20 carbon atoms, a hydroxyl group, an alkoxy group having 1 to 20carbon atoms or a halogen atom.

The repeating unit [2] is more preferably a repeating unit [3]represented by the following formula (3):

wherein R³ is a hydrogen atom or an alkyl group having 1 to 20 carbonatoms, and R⁴ to R¹⁴ are, independently of one another, a hydrogen atom,an alkyl group having 1 to 20 carbon atoms, a hydroxyl group, an alkoxygroup having 1 to 20 carbon atoms or a halogen atom.

An typical example of the repeating unit [3] is a repeating unit [4]represented by the following formula

The weight average molecular weight (Mw) of the vinyl alicyclichydrocarbon polymer is within a range of generally 10,000 to 1,000,000,preferably 50,000 to 500,000, more preferably 100,000 to 300,000 interms of polystyrene as determined by gel permeation chromatography(GPC). The molecular weight distribution expressed by a ratio (Mw/Mn) ofthe weight average molecular weight (Mw) to the number average molecularweight (Mn) is generally 5 or lower, preferably 3 or lower, morepreferably 2.5 or lower, most preferably 2 or lower. The vinyl alicyclichydrocarbon polymer becomes excellent in mechanical strength and heatresistance when the molecular weight distribution (Mw/Mn) thereof fallswithin the above range, and excellent in the balance among strengthproperties, forming or molding ability and low birefringence when theweight average molecular weight (Mw) falls within the above range.

The glass transition temperature (Tg) of the vinyl alicyclic hydrocarbonpolymer is within a range of generally 50 to 250° C., preferably 70 to200° C., more preferably 90 to 180° C.

In the present invention, specific example of the vinyl aromaticcompound usable as a monomer include styrene and derivatives thereofsuch as styrene, α-methylstyrene, α-ethylstyrene, α-propylstyrene,α-isopropylstyrene, α-t-butylstyrene, 2-methylstyrene, 3-methylstyrene,4-methylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene,4-t-butylstyrene, 5-t-butyl-2-methylstyrene, monochlorostyrene,dichlorostyrene, monofluorostyrene and 4-phenylstyrene.

Specific examples of the vinyl alicyclic hydrocarbon compound usable asa monomer include vinylcyclohexane and derivatives thereof such asvinylcyclohexane and 3-methylisopropenylcyclohexane; andvinylcyclohexene and derivatives thereof such as 4-vinylcyclohexene,4-isopropenylcyclohexene, 1-methyl-4-vinylcyclohexene,1-methyl-4-isopropenylcyclohexene, 2-methyl-4-vinylcyclohexene and2-methyl-4-isopropenylcyclohexene.

In the present invention, any other monomer copolymerizable with theabove-mentioned monomers may be copolymerized. Examples of thecopolymerizable monomer include α-olefin monomers such as ethylene,propylene, isobutene, 2-metyl-1-buten, 2-methyl-1-pentene and4-methyl-1-pentene; cyclopentadiene monomers such as cyclopentadiene,1-methyl-cyclopentadiene, 2-methylcyclopentadiene,2-ethyl-cyclopentadiene, 5-methylcyclopentadiene,5,5-dimethyl-cyclopentadiene and dicyclopentadiene; monocyclic olefinmonomers such as cyclobutene, cyclopentene and cyclohexene; conjugateddiene monomers such as butadiene, isoprene, 1,3-pentadiene, furan,thiophene and 1,3-cyclohexadiene; nitrile monomers such asacrylonitrile, methacrylonitrile and α-chloroacrylonitrile;(meth)acrylic ester monomers such as methyl methacrylate, ethylmethacrylate, propyl methacrylate, butyl methacrylate, methyl acrylate,ethyl acrylate, propyl acrylate and butyl acrylate; unsaturated fattyacid monomers such as acrylic acid, methacrylic acid and maleicanhydride; phenylmaleimide; methyl vinyl ether; heterocycle-containingvinyl compound monomers such as N-vinylcarbazole andN-vinyl-2-pyrrolidone.

The mixture of the above-described monomers used in the polymerizationpreferably contains a vinyl aromatic compound and/or a vinyl alicyclichydrocarbon compound in a proportion of generally at least 50%,preferably at least 70%, more preferably at least 80% from theviewpoints of heat resistance, low birefringence and mechanicalstrength. The monomer mixture may contain both vinyl aromatic compoundand vinyl alicyclic hydrocarbon compound.

The polymer used in the present invention is obtained by any publiclyknown process such as radical polymerization, anionic polymerization orcationic polymerization. In the case of the anionic polymerization orcationic polymerization, anionic living polymerization or cationicliving polymerization may also be adopted. As a form of thepolymerization, any polymerization method such as bulk polymerization,emulsion polymerization, suspension polymerization or solutionpolymerization may be used. In the case where a hydrogenation reactionis conducted subsequently, however, the solution polymerization ispreferred because the hydrogenation reaction can be continuouslyconducted.

The radical polymerization may be conducted in accordance with anypublicly known process. The cationic polymerization may be conducted inthe publicly known process making use of BF₃ or PF₆. In order to obtaina polymer having a high molecular weight and a narrow molecular weightdistribution, the anionic living polymerization is preferably adopted.More specifically, the polymerization is conducted by using an organicalkali metal as an initiator in a hydrocarbon solvent. The polymerobtained by the anionic living polymerization has a high molecularweight and a narrow molecular weight distribution and is excellent inmechanical strength.

After the polymerization reaction, the polymer can be collected by anypublicly known method such as a steam stripping method, direct desolventmethod or alcoholic solidification method. When a solvent inert to thehydrogenation reaction is used in the polymerization, the resultingpolymer can be used in the next hydrogenation reaction step as it iswithout collecting it from a polymer solution.

No particular limitation is imposed on a hydrogenation process, and thehydrogenation can be conducted in accordance with a process known per sein the art. More specifically, when the hydrogenation reaction isconducted by, for example, using a hydrogenation catalyst containing atleast one metal selected from the group consisting of nickel, cobalt,iron, titanium, rhodium, platinum, ruthenium and rhenium in an organicsolvent, the rate of hydrogenation can be raised, and breaking of apolymer chain attendant on the hydrogenation reaction can be prevented.The use of a nickel catalyst among these hydrogenation catalysts ispreferred because the molecular weight distribution (Mw/Mn) of theresulting hydrogenated polymer can be narrowed. The hydrogenationcatalyst may be either a heterogeneous catalyst or a homogeneouscatalyst.

The hydrogenation reaction is performed by controlling a reactiontemperature within a range of generally 10 to 250° C., preferably 50 to200° C., more preferably 80 to 180° C. under a hydrogen pressure ranginggenerally from 1 to 300 kg/cm², preferably from 5 to 250 kg/cm², morepreferably from 10 to 200 kg/cm².

The rate of hydrogenation of the hydrogenated polymer obtained by theabove-described process is generally at least 80%, preferably at least90%, more preferably at least 95%.

In the present invention, a block copolymer can be used as the vinylalicyclic hydrocarbon polymer. The block copolymer used in the presentinvention has the following polymer block [A] and polymer block [B].

The polymer block [A] is a polymer block containing repeating units [3]represented by the following formula (3):

wherein R³ is a hydrogen atom or an alkyl group having 1 to 20 carbonatoms, and R⁴ to R¹⁴ are, independently of one another, a hydrogen atom,an alkyl group having 1 to 20 carbon atoms, a hydroxyl group, an alkoxygroup having 1 to 20 carbon atoms or a halogen atom. The content of therepeating units [3] in the polymer block [A] is generally at least 50mol %, preferably at least 70 mol %, more preferably at least 90 mol %.

In the repeating unit [3] represented by the formula (3), it ispreferred that R³ be a hydrogen atom or methyl group, and R⁴ to R¹⁴ behydrogen atoms, and it is more preferred that R³ and R⁴ to R¹⁴ behydrogen atoms.

Accordingly, the repeating unit [3] is more preferably a repeating unit[4] represented by the following formula (4):

If the content of the repeating units [3] in the polymer block [A] istoo low, the mechanical strength of such a block copolymer isdeteriorated. The content of the repeating units [3] within the aboverange is preferred because the block copolymer becomes excellent in lowbirefringence, light transmission property and mechanical strength.

The remaining portions other than the repeating units [3] in the polymerblock [A] are repeating units derived from a linear conjugated dieneand/or a linear vinyl compound (for example, α-olefin monomer).

The polymer block [B] is a polymer block containing repeating units [5]represented by the following formula (5):

wherein R¹⁵ is a hydrogen atom or an alkyl group having 1 to 20 carbonatoms, and/or repeating units [6] represented by the following formula(6):

wherein R¹⁶ to R¹⁷ are, independently of each other, a hydrogen atom oran alkyl group having 1 to 20 carbon atoms.

The polymer block [B] may contain the repeating units [3]. The contentof the repeating units [3] in the polymer block [B] is within a range offrom at most the content of the repeating units [3] in the polymer block[A] back to at least 0 mol %. When the content of the repeating units[3] in the polymer block [B] is high, the transparency and heatresistance of the block copolymer are improved. When the content is low,the impact resistance and break strength properties are improved. Thecontent of the repeating units [3] in the polymer block [B] is selectedin such a manner that the block copolymer has suitable propertiesaccording to the end application thereof.

Supposing that a mole fraction of the repeating units [5] in the polymerblock [B] is m₂ (mol %), and a mole fraction of the repeating units [6]is m₃ (mol %), 2×m₂+m₃ amounts to generally at least 2 mol %, preferably5 to 100 mol %, more preferably 30 to 100 mol %.

In the repeating unit [5] represented by the formula (5), it ispreferred that R¹⁵ be a hydrogen atom or methyl group. In the repeatingunit [6] represented by the formula (6), it is preferred that R¹⁶ be ahydrogen atom or methyl group, and R¹⁷ be a methyl group or ethyl group.

If the content of the repeating units [5] and/or the repeating units [6]in the polymer block [B] is too low, the mechanical strength of theblock copolymer is deteriorated. The content of the repeating units [5]and/or the repeating units [6] within the above range in the polymerblock [B] is preferred because the block copolymer becomes excellent inlow birefringence, light transmission property and mechanical strength.

The polymer block [B] may further contain repeating units [7]represented by the following formula (7):

wherein R¹⁸ is a hydrogen atom or an alkyl group having 1 to 20 carbonatoms, R¹⁹ is a nitrile group, alkoxycarbonyl group, hydrocarbonylgroup, hydroxycarbonyl group or halogen atom, and R²⁰ is a hydrogenatom, with the proviso that R¹⁹ and R²⁰ may be boned to each other toform an acid anhydride group or amide group.

The content of the repeating units [7] is an amount in such a range thatthe properties of the block copolymer used in the present invention isnot impaired, and is generally at most 30 mol %, preferably at most 20mol %.

When the block copolymer used in the present invention further containsthe repeating units [3] in the polymer block [B], it is preferred that amole fraction a (mol %) of the repeating units [3] in the polymer block[A] and a mole fraction b (mol %) of the repeating units [3] in thepolymer block [B] satisfy the relationship of a>b. It is preferred thata>b be satisfied, since the resulting block copolymer become excellentin low birefringence, light transmission property and mechanicalstrength.

In the block copolymer used in the present invention, it is desirablethat supposing that the number of moles of the whole repeating unitforming the block [A] is m_(a), and the number of moles of the wholerepeating unit forming the block [B] is m_(b), a ratio (m_(a):m_(b))thereof be generally 4:96 to 96:4, preferably 30:70 to 95:5, morepreferably 40:60 to 90:10. It is preferred that the ratio (m_(a):m_(b))falls within the above range, since the block copolymer becomesexcellent in mechanical strength and heat resistance.

The total content of the repeating units [3] in the block copolymer isgenerally at least 50% by weight, preferably at least 70% by weight.

The block copolymer used in the present invention may be any of diblock,triblock and multi-block copolymers composed of the polymer blocks [A]and [B]. The chain of each block may be not only linear, but also have abranched structure such as a star form. Further, when the polymer blocks[A] and [B] forming the block copolymer are respectively present morethan one, they may be the same or different from each other so far asthe above-described conditions are satisfied.

The molecular weight of the block copolymer is within a range ofgenerally 10,000 to 1,000,000, preferably 10,000 to 300,000, morepreferably 15,000 to 250,000, particularly preferably 20,000 to 200,000when expressed by a weight average molecular weight (Mw) in terms ofpolystyrene as determined by GPC. It is preferred that the weightaverage molecular weight (Mw) of the block polymer falls within theabove range, since the block copolymer becomes excellent in the balanceamong mechanical strength, heat resistance and forming or moldingability.

The molecular weight distribution of the block copolymer may be suitablyselected as necessary for the end application intended. The molecularweight distribution (Mw/Mn) expressed by a ratio of the weight averagemolecular weight (Mw) to the number average molecular weight (Mn) interms of polystyrene as measured by GPC is generally 5 or lower,preferably 4 or lower, more preferably 3 or lower. It is preferred thatthe molecular weight distribution (Mw/Mn) falls within the above range,since the block copolymer becomes excellent in mechanical strength andheat resistance.

The glass transition temperature (Tg) of the block copolymer may besuitably selected as necessary for the end application intended.However, it is generally 70 to 150° C., preferably 80 to 140° C., morepreferably 90 to 130° C. in terms of a measured value on ahigh-temperature side by a differential scanning calorimeter (DSC).

The block copolymer used in the present invention can be obtained inaccordance with, for example, the following preparation process (I) or(II).

Preparation Process (I) of Block Copolymer:

A preparation process comprising synthesizing a block copolymer having apolymer block [A′] and a polymer block [B′] through at least two stepsof:

-   -   polymerizing a monomer mixture [a′] containing at least 50 mol %        of a vinyl aromatic compound and/or a vinyl alicyclic        hydrocarbon compound having an unsaturated bond in its ring to        obtain the polymer block [A′] containing repeating units derived        from the vinyl aromatic compound and/or the vinyl alicyclic        hydrocarbon compound having an unsaturated bond in its ring; and    -   polymerizing a monomer mixture (b′) containing at least 2 moles        of a vinyl monomer (linear conjugated diene and/or linear vinyl        compound) and optionally containing a vinyl aromatic compound        and/or a vinyl alicyclic hydrocarbon compound having an        unsaturated bond in its ring in a proportion lower than the        proportion in the monomer composition [a′] described above to        obtain the polymer block [B′] containing repeating units derived        from the vinyl monomer and repeating units derived from the        vinyl aromatic compound and/or the vinyl alicyclic hydrocarbon        compound having an unsaturated bond in its ring, and        hydrogenating the aromatic rings and/or unsaturated alicyclic        rings in the block copolymer. Preparation process (II) of block        copolymer:

A preparation process comprising preparing a block copolymer having apolymer block [A] and a polymer block [B] through at least two steps of:

-   -   polymerizing a monomer mixture [a]containing at least 50 mol %        of a vinyl alicyclic hydrocarbon compound having a saturated        alicyclic ring to obtain the polymer block [A] containing        repeating units derived from the vinyl alicyclic hydrocarbon        compound; and    -   polymerizing a monomer mixture (b) containing at least 2 moles        of a vinyl monomer and optionally containing a vinyl alicyclic        hydrocarbon compound having a saturated alicyclic ring in a        proportion lower than the proportion in the monomer composition        [a]described above to obtain the polymer block [B] containing        repeating units derived from the vinyl monomer and repeating        units derived from the vinyl alicyclic hydrocarbon compound.

Among the above-described processes, the preparation process (I) ispreferred from the viewpoints of availability of the monomers,polymerization yield, easy introduction of the repeating units [3] intothe polymer block [B′], etc.

Specific examples of the vinyl aromatic compound used in the preparationprocess (I) of the block copolymer include styrene and derivativesthereof such as styrene, α-methylstyrene, α-ethylstyrene,α-propylstyrene, α-isopropylstyrene, α-t-butylstyrene, 2-methylstyrene,3-methylstyrene, 4-methylstyrene, 2,4-diisopropylstyrene,2,4-dimethylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene,monochlorostyrene, dichlorostyrene, monofluorostyrene and4-phenylstyrene. Styrene derivatives having a subsistent group such as ahydroxyl group or alkoxyl group may also be used. Among these, styrene,2-methylstyrene, 3-methylstyrene and 4-methylstyrene are preferred.

Specific examples of the vinyl alicyclic hydrocarbon compound having anunsaturated alicyclic ring used in the preparation process (I) of theblock copolymer include cyclohexenylethylene (i.e., vinylcyclohexene)and derivatives thereof such as cyclohexenylethylene,α-methylcyclohexenylethylene and α-t-butylcyclohexenyl-ethylene; andcyclohexenylethylene derivatives having a subsistent group such as ahalogen group, alkoxy group or hydroxyl group.

These vinyl aromatic compounds and vinyl alicyclic hydrocarbon compoundshaving an unsaturated alicyclic ring may be used either singly or in anycombination thereof. In the present invention, the vinyl aromaticcompound is preferably caused to be contained in both monomer mixtures[a′] and [b′]. In particular, styrene or α-methylstyrene is morepreferably used.

The vinyl monomer used in the preparation processes is a linear vinylcompound or linear conjugated diene compound.

Specific examples of the linear vinyl compound include α-olefin monomerssuch as ethylene, propylene, 1-butene, 1-pentene and 4-methyl-1-pentene.Among these, ethylene, propylene and 1-butene are preferred.

Examples of the linear conjugated diene compound include conjugateddiene monomers such as butadiene (for example, 1,3-butadiene and1,2-butadiene), isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and1,3-hexadiene.

Among the vinyl monomers, the linear conjugated diene compounds arepreferred, with butadiene and isoprene being particularly preferred.These linear vinyl compounds and linear conjugated diene compounds maybe used either singly or in any combination thereof.

When the monomer mixture is polymerized, a polymerization reaction maybe conducted by any process of radical polymerization, anionicpolymerization, cationic polymerization, etc. However, the anionicpolymerization is preferred, with living anionic polymerization in thepresence of an inert solvent being more preferred.

The anionic polymerization is performed in a temperature range ofgenerally 0 to 200° C., preferably 20 to 100° C., particularlypreferably 20 to 80° C. in the presence of a polymerization initiator.As the initiator, may be used, for example, a mono-organolithium such asn-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium orphenyllithium; or a polyfunctional organolithium compound such asdilithiomethane, 1,4-dilithobutane or 1,4-dilithio-2-ethylcyclohexane.

Examples of the inert solvent used include aliphatic hydrocarbons suchas n-butane, n-pentane, isopentane, n-hexane, n-heptane and isooctane;alicyclic hydrocarbons such as cyclopentane, cyclohexane,methylcyclopentane, methylcyclohexane and decalin; and aromatichydrocarbons such as benzene and toluene. When an aliphatic hydrocarbonor alicyclic hydrocarbon among these is used as the solvent, theresulting reaction mixture may be used in the next hydrogenationreaction as it is because the solvent is a solvent inert to thehydrogenation reaction as well. These solvents may be used either singlyor in any combination thereof. The solvent is generally used in aproportion of 200 to 10,000 parts by weight per 100 parts by weight ofthe whole monomer.

When it is necessary to prevent a chain of a certain component in eachblock from elongating upon polymerization of each polymer block, apolymerization promoter, randomizer or the like may be used. When thepolymerization reaction is conducted by anionic polymerization, a Lewisbase compound or the like may be used as the randomizer.

Specific examples of the Lewis base compound include ether compoundssuch as dimethyl ether, diethyl ether, diisopropyl ether, dibutyl ether,tetrahydrofuran, diphenyl ether, ethylene glycol diethyl ether andethylene glycol methyl phenyl ether; tertiary amine compounds such astetramethylenediamine, trimethylamine, triethylamine and pyridine;alkali metal alkoxide compounds such as potassium-t-amyl oxide andpotassium-t-butyl oxide; and phosphine compounds such astriphenylphosphine. These Lewis bases may be used either singly or inany combination thereof.

Examples of a process for obtaining the block copolymer by livinganionic polymerization include the conventionally known stepwiseaddition polymerization reaction process and coupling process. Thestepwise addition polymerization reaction process is preferred.

When the block copolymer having the polymer block [A′] and the polymerblock [B′] is obtained by the stepwise addition polymerization reactionprocess, the step of obtaining the polymer block [A′] and the step ofobtaining the polymer block [B′] are successively continuouslyperformed. Specifically, the monomer mixture [a′] is polymerized in thepresence of a living anionic polymerization catalyst in an inert solventto synthesize the polymer block [A′], and the monomer mixture [b′] issuccessively added to the reaction system thereof to continue thepolymerization to obtain the polymer block [B′] bonded to the polymerblock [A′]. Similarly, a block copolymer having a structure of PolymerBlock [A′]-Polymer Block [B′]-Polymer Block [A′] can by synthesized.

The resultant block copolymer is collected by a publicly known method,for example, a steam stripping method, direct desolvent method oralcoholic solidification method. When a solvent inert to a hydrogenationreaction is used in the polymerization reaction, the reaction mixturecan be used in the next hydrogenation reaction step as it is. Therefore,the block copolymer may not be collected at this step.

Among the block copolymers (hereinafter referred to as “prehydrogenationblock copolymers”) having the polymer block [A′] and the polymer block[B′], those having respective repeating units of the followingstructures are preferred.

The polymer block [A′] forming the prehydrogenation block copolymers ispreferably a polymer block containing at least 50 mol % of repeatingunits [8] represented by the following formula (8):

wherein R²¹ is a hydrogen atom or an alkyl group having 1 to 20 carbonatoms, and R²² to R²⁶ are, independently of one another, a hydrogenatom, an alkyl group having 1 to 20 carbon atoms, a hydroxyl group, analkoxy group having 1 to 20 carbon atoms or a halogen atom.

In the repeating unit [8], it is preferred that R²¹ be a hydrogen atomor methyl group, and R²² to R²⁶ be hydrogen atoms, and it is morepreferred that R²¹ and R²² to R²⁶ be hydrogen atoms.

Accordingly, the repeating unit [8] is more preferably a repeating unit[9] represented by the following formula (9):

The polymer block [B′] is preferably a polymer block optionallycontaining the repeating units [8] and containing repeating units [10]represented by the following formula (10):

wherein R²⁷ is a hydrogen atom or an alkyl group having 1 to 20 carbonatoms, and/or a polymer block containing repeating units [11]represented by the following formula (11):

wherein R²⁸ is a hydrogen atom or an alkyl group having 1 to 20 carbonatoms, and R²⁹ is a hydrogen atom or an alkyl or alkenyl group having 1to 20 carbon atoms.

When the repeating units [8] is contained in the polymer block [B′], itis preferred that a mole fraction a′ (mol %) of the repeating units [8]in the polymer block [A′] and a mole fraction b′ (mol %) of therepeating units [8] in the polymer block [B′] satisfy the relationshipof a′>b′.

The polymer block [B′] may further contain repeating units [12]represented by the following formula (12):

wherein R³⁰ is a hydrogen atom or an alkyl group having 1 to 20 carbonatoms, R³¹ is a nitrile group, alkoxycarbonyl group, hydrocarbonylgroup, hydroxycarbonyl group or halogen atom, and R³² is a hydrogenatom, with the proviso that R³¹ and R³² may be boned to each other toform an acid anhydride group or amide group.

In the prehydrogenation block copolymer, it is desirable that supposingthat the number of moles of the whole repeating unit forming the block[A′] is m_(a)′, and the number of moles of the whole repeating unitforming the block [B] is m_(b)′, a ratio (m_(a)′:m_(b)′) thereof begenerally 4:96 to 96:4, preferably 30:70 to 95:5, more preferably 40:60to 90:10. It is preferred that the ratio (m_(a)′:m_(b)′) falls withinthe above range, since the finally obtained block copolymer becomesexcellent in mechanical strength and heat resistance.

The molecular weight of the prehydrogenation block copolymer isgenerally at least 12,000, preferably within a range of 12,000 to400,000, more preferably 19,000 to 350,000, particularly preferably25,000 to 300,000 when expressed by a weight average molecular weight(Mw) in terms of polystyrene as determined by GPC. When the weightaverage molecular weight (Mw) of the prehydrogenation block polymer istoo low, the mechanical strength of the block copolymer obtained afterthe hydrogenation is deteriorated. If the molecular weight is too high,it is difficult to fully raise the rate of hydrogenation.

The molecular weight distribution of the prehydrogenation blockcopolymer may be suitably selected as necessary for the end applicationintended. However, the molecular weight distribution (Mw/Mn) expressedby a ratio of the weight average molecular weight (Mw) to the numberaverage molecular weight (Mn) in terms of polystyrene (or polyisoprene)as measured by GPC is preferably 5 or lower, more preferably 4 or lower,particularly preferably 3 or lower. When the molecular weightdistribution (Mw/Mn) of the prehydrogenation block copolymer fallswithin the above range, the rate of hydrogenation is enhanced.

The glass transition temperature (Tg) of the prehydrogenation blockcopolymer may be suitably selected as necessary for the end applicationintended. However, it is preferably 70 to 150° C., more preferably 80 to140° C., particularly preferably 90 to 130° C. in terms of a measuredvalue on a high-temperature side by a differential scanning calorimeter(DSC).

No particular limitation is imposed on a process for hydrogenatingcarbon-carbon unsaturated bonds in unsaturated rings of theprehydrogenation block copolymer, such as aromatic rings and cycloalkenerings, and unsaturated bonds in main and side chains, and thehydrogenation can be conducted in accordance with such a publicly knownprocess as described above. Here, reaction conditions suitable forhydrogenation of the prehydrogenation block copolymer will be described.

As the hydrogenation process, is preferred a process by which the rateof hydrogenation can be raised, and a breaking reaction of a polymerchain is little. As a specific example thereof, may be mentioned aprocess making use of a hydrogenation catalyst containing at least onemetal selected from the group consisting of nickel, cobalt, iron,titanium, rhodium, platinum, ruthenium and rhenium in an organicsolvent, As the hydrogenation catalyst, may be used either aheterogeneous catalyst or a homogeneous catalyst.

The heterogeneous catalyst may be used in the form of a metal or a metalcompound or in a form carried on a proper support. Examples of thesupport include activated carbon, silica, alumina, calcium carbonate,titania, magnesia, zirconia, diatomaceous earth and silicon carbide. Theamount of the catalyst carried is within a range of generally 0.01 to80% by weight, preferably 0.05 to 60% by weight.

As the homogeneous catalyst, may be used a catalyst with a nickel,cobalt, titanium or iron compound combined with an organometalliccompound (for example, organoaluminum compound or organolithiumcompound); or an organometallic complex of rhodium, palladium, platinum,ruthenium, rhenium or the like. As the nickel, cobalt, titanium or ironcompound, may be used, for example, an acetylacetone salt, naphthenicacid salt or cyclopentadienyl compound of each of such metals. As theorganoaluminum compound, may be suitably used an alkylaluminum such astriethylaluminum or triisobutylaluminum; an aluminum halide such asdiethylaluminum chloride or ethylaluminum dichloride; or a hydrogenatedalkylaluminum such as diisobutylaluminum hydride.

As examples of the organometallic complex catalyst, may be used metalcomplexes such as γ-dichloro-π-benzene complexes,dichloro-tris(triphenylphosphine) complexes andhydride-chloro-(triphenylphosphine) complexes of the above respectivemetals.

These hydrogenation catalysts may be used either singly or in anycombination thereof. The amount of the hydrogenation catalyst used isgenerally 0.01 to 100 parts by weight, preferably 0.05 to 50 parts byweight, more preferably 0.1 to 30 parts by weight per 100 parts byweight of the polymer.

The reaction temperature in the hydrogenation is generally 10 to 250° C.However, it is preferably 50 to 200° C., more preferably 80 to 180° C.in that the rate of hydrogenation can be raised, and a breaking reactionof a polymer chain can be lessened.

The pressure in the hydrogenation is generally 0.1 to 30 Mpa. However,it is selected from a range of preferably 1 to 20 Mpa, more preferably 2to 10 Mpa from the viewpoint of operating ability in addition to thereasons described above.

The rate of hydrogenation of the block copolymer obtained by thehydrogenation reaction is generally at least 90%, preferably at least95%, more preferably at least 97% for both carbon-carbon unsaturatedbonds in the main and side chains and carbon-carbon unsaturated bonds inthe aromatic and cycloalkene rings as determined by ¹H-NMR. When therate of hydrogenation is low, the resulting block copolymer tends todeteriorate the low birefringence, heat stability, etc.

After completion of the hydrogenation reaction, the block copolymer iscollected in accordance with, for example, a method in which the solventis removed by direct drying, or a method in which the reaction solutionis poured into a poor solvent to the block copolymer to solidify theblock copolymer after the hydrogenation catalyst is removed from thereaction solution by a method of filtration, centrifugation or the like.

2. Hindered Amine Light-resistance Stabilizer:

The hindered amine light-resistance stabillzer (hereinafter abbreviatedas “HALS”) used in the present invention is a compound having aplurality of piperidine rings with substituent group(s) bonded to bothcarbon atoms adjacent to the nitrogen atom. In the present invention, isused HALS having a number average molecular weight (Mn) of 1,000 to10,000, preferably 2,000 to 5,000, more preferably 2,800 to 3,800 asdetermined by GPC using tetrahydrofuran (THE) as a solvent.

The subsistent groups bonded to the carbon atoms adjacent to thenitrogen atom are preferably alkyl groups such as methyl and ethylgroups. The stabilizer is more preferably such that 2 methyl groups arebonded to each of the carbon atoms.

If the number average molecular weight (Mn) of HALS is too low, HALS isvaporized upon mixing it into the vinyl alicyclic hydrocarbon polymer bymelting and kneading under heat to fail to mix it in a prescribedamount, or a cause that foaming or silver streak occurs upon heating andmelt molding by injection molding is formed to deteriorate theprocessing stability of the resulting resin composition.

If the number average molecular weight (Mn) of HALS is too low, avolatile component is generated as a gas from a light guide plateobtained by molding a resin composition incorporating HALS when thelight guide plate is used for a long period of time in a state that alamp has been lighted.

If the number average molecular weight (Mn) of HALS is too high, itsdispersibility in the vinyl alicyclic hydrocarbon polymer isdeteriorated to lower the transparency of the resulting resincomposition and reduce the improving effect on light resistance. Thenumber average molecular weight (Mn) of HALS is controlled within theabove range, thereby obtaining a resin composition excellent inprocessing stability, low gas generating tendency and transparency.

Examples of HALS preferably used in the present invention include highmolecular weight HALSs with a plurality of piperidine rings bondedthrough a triazine skeleton, such as

N,N′,N″,N′″-tetrakis-[4,6-bis-[butyl-(N-methyl-2,2,6,6-tetramethylpyridin-4-yl)amino]-triazin-2-yl]-4,7-diazadecane-1,10-diamine,

polycondensates of dibutylamine, 1,3,5-triazine andN,N′-bis(2,2,6,6-tetramethyl-4-piperidyl)butylamine,

poly[{(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazin-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}-hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}],

polycondensates of1,6-hexanediamine-N,N′-bis(2,2,6,6-tetramethyl-4-piperidyl) andmorpholine-2,4,6-trichloro-1,3,5-triazine, and

poly[(6-morpholino-s-triazin-2,4-diyl)[(2,2,6,6-tetramethyl-4-piperidyl)imino]-hexamethylene[(2,2,6,6-tetramethyl-4-piperidyl)imino]];and

high molecular weight HALSs with piperidine rings bonded through anester linkage, such as

polymers of dimethyl succinate and4-hydroxy-2,2,6,6-tetramethyl-1-piperidine ethanol, and

mixed ester compounds of 1,2,3,4-butanetetracarboxylic acid,1,2,2,6,6-pentamethyl-4-piperidinol and3,9-bis(2-hydroxy-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro[5,5]undecane.

Among these, the polycondensates of dibutylamine, 1,3,5-triazine andN,N′-bis(2,2,6,6-tetramethyl-4-piperidyl)butylamine,poly[{(1,1,3,3-tetramethylbutyl)-amino-1,3,5-triazin-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}-hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}]and polymers of dimethyl succinate and4-hydroxy-2,2,6,6-tetramethyl-1-piperidine ethanol which have a numberaverage molecular weight (Mn) of 2,000 to 5,000 are preferred.

HALS is incorporated within a range of generally 0.01 to 20 parts byweight, preferably 0.02 to 15 parts by weight, more preferably 0.05 to10 parts by weight per 100 parts by weight of the vinyl alicyclichydrocarbon polymer. If the amount of HALS incorporated is too small,the improving effect on light-resistance stability is not sufficientlyachieved, and so coloring occurs when a light guide plate formed with aresin composition incorporating such HALS is used in a long period oftime in a state that a lamp has been lighted. If the amount of HALSincorporated is too great, a part thereof is vaporized as a gas, and itsdispersibility in the vinyl alicyclic hydrocarbon polymer isdeteriorated to lower the transparency of the resulting resincomposition.

HALS preferably has a melting point of at least 20° C., more preferablyat least 40° C. If the melting point of HALS is too low, the viscosityof a molten resin is lowered to an excessive extent when it is heatedand melt kneaded into the vinyl alicyclic hydrocarbon polymer by meansof a twin-screw kneader or the like, and so such problems that HALS isnot evenly dispersed in the molten resin arise.

3. Ultraviolet Absorbent:

The resin composition according to the present invention can be furtherimproved in light-resistance stability by using HALS and an ultravioletabsorbent in combination.

Examples of the ultraviolet absorbent include benzophenone typeultraviolet absorbents such as 2,4-dihydroxybenzophenone,2-hydroxy-4-methoxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone,2,2′-dihydroxy-4,4′-dimethoxybenzophenone,2-hydroxy-4-methoxy-2′-benzophenone,2-hydroxy-4-methoxy-5-sulfobenzophenone trihydrate,2-hydroxy-4-n-octoxybenzophenone, 2,2′,4,4′-tetrahydroxy-benzophenone,4-dodecyloxy-2-hydroxybenzophenone andbis(5-benzoyl-4-hydroxy-2-methoxyphenyl)methane; and benzotriazole typeultraviolet absorbents such as2-(2′-hydroxy-5′-methylphenyl)benzotriazole,2-(2H-benzotriazol-2-yl)-4-methyl-6-(3,4,5,6-tetrahydrophthalimidylmethyl)-phenol,2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol,2-(2′-hydroxy-3′,5′-di-tert-butylphenyl)benzotriazole,2-(2′-hydroxy-3′-tert-butyl-5′-methylphenyl)-5-chlorobenzotriazole,2-(2′-hydroxy-5′-tert-octylphenyl)benzotriazole,2-(2′-hydroxy-3′,5′-di-tert-amylphenyl)benzotriazole,2-[2′-hydroxy-3′-(3″,4″,5″,6″-tetrahydrophthalimidomethyl)-5′-methylphenyl]benzotriazoleand2,2′-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol].

Among these, 2-(2′-hydroxy-5′-methylphenyl)-benzotriazole,2-(2H-benzotriazol-2-yl)-4-methyl-6-(3,4,5,6-tetrahydrophthalimidylmethyl)phenoland 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol arepreferred from the viewpoints of heat resistance, low volatility, etc.

The ultraviolet absorbent is incorporated within a range of generally0.01 to 10 parts by weight, preferably 0.02 to 5 parts by weight, morepreferably 0.05 to 2 parts by weight per 100 parts by weight of thevinyl alicyclic hydrocarbon polymer. If the amount of the ultravioletabsorbent incorporated is too small, the further improving effect onlight-resistance stability is not sufficiently achieved. If the amountof the ultraviolet absorbent incorporated is too great, the processingstability of the resulting resin composition is deteriorated, and theresin composition is liable to generate gases.

4. Other Compounding Additives:

Into the vinyl alicyclic hydrocarbon polymer according to the presentinvention, may be incorporated various kinds of compounding additivessuch as antioxidants and ultraviolet absorbents as needed.

Examples of the antioxidants include phenolic antioxidants, phosphorusantioxidants and sulfur antioxidants. Among these, the phenolicantioxidants, particularly, alkyl-substituted phenolic antioxidants arepreferred. These antioxidants are incorporated, whereby coloring andreduction of strength of the resulting light guide plate due todeterioration by oxidation upon molding or forming can be preventedwithout impairing the transparency and low water absorption propertythereof.

The amount of the antioxidant incorporated is suitably selected withinlimits not impeding the objects of the present invention. However, it isgenerally 0.001 to 5 parts by weight, preferably 0.01 to 1 part byweight per 100 parts by weight of the vinyl alicyclic hydrocarbonpolymer.

At least one compounding additive selected from the group consisting of(i) a soft polymer, (ii) an alcoholic compound and (iii) an organic orinorganic filler is incorporated into the vinyl alicyclic hydrocarbonpolymer, whereby clouding of the resulting resin composition whenexposed for a long period of time under high-temperature andhigh-humidity environment can be prevented without deteriorating variousproperties such as transparency, low water absorption property andmechanical strength.

Among these, the soft polymer and alcoholic compound are preferredbecause they are excellent in clouding preventing ability under thehigh-temperature and high-humidity environment.

(i) Soft Polymer:

The soft polymer used in the present invention is a polymer having aglass transition temperature (Tg) of generally at most 30° C. When apolymer has a plurality of Tgs, such a polymer may also be included inthe soft polymer so far as its lowest Tg is at most 30° C.

As specific examples of the soft polymers, may be mentioned olefin-basedsoft polymers such as polyethylene, polypropylene, poly(1-butene),ethylene.α-olefin copolymers, propylene.α-olefin copolymers,ethylene.propylene.diene terpolymers (EPDMs) andethylene.propylene.styrene copolymers; isobutyrene-based soft polymerssuch as polyisobutylene, isobutylene.isoprene rubber andisobutylene.styrene copolymers; diene-based soft polymers such aspolybutadiene, polyisoprene, butadiene.styrene random copolymers,isoprene.styrene random copolymers, acrylonitrile.butadiene copolymers,acrylonitrile.butadiene.styrene terpolymers, butadiene.styrene blockcopolymers, styrene.butadiene.styrene block copolymers, isoprene.styreneblock copolymers and styrene.isoprene.styrene block copolymers;silicon-containing soft polymers such as dimethyl polysiloxane, diphenylpolysiloxane and dihydroxy polysiloxane; soft polymers composed of anα,β-unsaturated acid, such as polybutyl acrylate, polybutylmethacrylate, polyhydroxyethyl methacrylate and butyl acrylate.styrenecopolymers; soft polymers composed of an unsaturated alcohol and anamine or an acyl derivative thereof, or acetal, such as polyvinylstearate; epoxy compound-based soft polymers such as polyethylene oxide,polypropylene oxide and epichlorohydrin rubber; fluorine-containing softpolymers such as vinylidene fluoride rubber and ethylenetetrafluoride-propylene rubber; and other soft polymers such as naturalrubber, polypeptide, proteins, polyester-based thermoplastic elastomers,vinyl chloride-based thermoplastic elastomers and polyamide-basedthermoplastic elastomers. These soft polymers may have a crosslinkedstructure or may be modified by introducing a functional group.

Among these soft polymers, the diene-based soft polymers are preferred,with hydrogenated products obtained by hydrogenating carbon-carbonunsaturated bonds in the diene-based soft polymers being particularlyexcellent in rubber elasticity, mechanical strength, flexibility anddispersibility.

(ii) Alcoholic compound:

The alcoholic compound suitably used in the present invention ispreferably a compound having at least one alcoholic hydroxyl group andat least one ether linkage or ester linkage in its molecule, with acompound having at least two alcoholic hydroxyl groups being morepreferred. Examples of such a compound include partially etherifiedcompounds and partially esterified compounds obtained by etherifying oresterifying at least one hydroxyl group of a dihydric or still higherpolyhydric alcohol.

Specific examples of the alcoholic compound include alcoholic esterifiedcompounds such as glycerol monostearate, glycerol monolaurate, glycerolmonobehenate, diglycerol monostearate, glycerol distearate, glyceroldilaurate, pentaerythritol monostearate, pentaerythoritol monolaurate,pentaerythoritol monobehenate, pentaerythoritol distearate,pentaerythoritol dilaurate, pentaerythoritol tristearate anddipentaerythoritol distearate; 3-(octyloxy)-1,2-propanediol,3-(decyloxy)-1,2-propanediol, 3-(lauryloxy)-1,2-propanediol,3-(4-nonylphenyhloxy)-1,2-propanediol,1,6-dihydroxy-2,2′-di(hydroxymethyl)-7-(4-nonylphenyloxy)-4-oxoheptane,alcoholic ether compounds obtained by a reaction of a condensate ofp-nonyl phenyl ether and formaldehyde with glycidol; alcoholic ethercompounds obtained by a reaction of a condensate of p-octyl phenyl etherand formaldehyde with glycidol; and alcoholic ether compounds obtainedby a reaction of a condensate of p-octyl phenyl ether anddicyclopentadiene with glycidol.

These alcoholic compounds may be used either singly or in anycombination thereof. No particular limitation is imposed on themolecular weight of the alcoholic compound. However, it is desirablethat the molecular weight be preferably 500 to 2000, more preferably 800to 1,500 in that the transparency of the resulting resin composition isscarcely lowered.

Said at least one compounding additive selected from the groupconsisting of (i) a soft polymer, (ii) an alcoholic compound and (iii)an organic or inorganic filler is incorporated in a range of generally0.1 to 10 parts by weight, preferably 0.02 to 5 parts by weight, morepreferably 0.05 to 2 parts by weight per 100 parts by weight of thevinyl alicyclic hydrocarbon polymer. These compounding additives areused in a proper amount, whereby clouding of a formed or molded articleformed from the resulting resin composition can be prevented withoutlowering the properties inherent in the vinyl alicyclic hydrocarbonpolymer. If the amount of these compounding additives incorporated istoo great, the glass transition temperature and transparency of theresin composition are lowered.

5. Resin Composition:

The resin composition according to the present invention can be preparedby, for example, melting and kneading the vinyl alicyclic hydrocarbonpolymer and various kinds of the components by means of a mixer,twin-screw kneader, roll, brabender or extruder, or dissolving ordispersing them in a proper solvent to solidify them. When thetwin-screw kneader is used, it is preferred that the resulting resincomposition be melt-extruded in the form of a strand after the kneading,and the strand be cut by a pelletizer to provide pellets.

The resin composition according to the present invention can be formedor molded into various kinds of formed or molded articles by a meltmolding or forming process such as injection molding, extrusion, pressmolding or blow molding. A solution casting process can also be adopted.In order to obtain a molded article excellent in transparency, lowbirefringence, dimensional stability, etc., the injection molding ispreferred.

The injection molding is performed under conditions of a resintemperature within a range of generally 150 to 400° C., preferably 200to 350° C., more preferably 230 to 330° C. If the resin temperature istoo low, the melt flowability of the resin composition is deteriorated,and the resulting molded article tends to cause sink mark anddistortion. If the resin temperature is too high, silver streak is easyto occur due to thermal decomposition of the resin, or the resultingmolded article is liable to be yellowed.

No particular limitation is imposed on the form of the formed or moldedarticle. As examples thereof, may be mentioned a rod, plate, sphere,column, cylinder, fiber, film and sheet. It is also permissible that theresin composition is coextruded with other resins, a formed or moldedarticle composed of he resin composition is laminated on anothermaterial, and a coating layer or deposit layer of another material isformed on a formed or molded article composed of he resin composition.

6. Light Guide Plate:

The resin composition according to the present invention is suitable foruse as a forming or molding material for light guide plates for planeemission illuminators in liquid crystal display devices. Morespecifically, the light guide plate according to the present inventioncan be obtained by forming or molding a resin composition obtained bymixing the vinyl alicyclic hydrocarbon polymer, HALS and optionallyvarious kinds of the compounding additives. As a forming or moldingprocess, may be adopted a heating and melt forming or molding processsuch as an injection molding process, extrusion process, press moldingprocess or blow molding process, or a solution casting process. Amongthese forming or molding processes, the injection molding process,extrusion process and press molding process are preferably used for thepurpose of obtaining a light guide plate excellent in transparency, andthe injection molding process is more preferred.

The form and size of the light guide plate may be suitably determined asneeded. A commonly used light guide plate has a thickness of generally0.05 to 6 mm, preferably 0.1 to 4 mm, a width of generally 50 to 400 mm,preferably 100 to 350 mm and a length of generally 50 to 350 mm,preferably 70 to 300 mm. The light guide plate may be in a tapered(wedge) form that the thickness is successively changed in thelongitudinal direction thereof.

EXAMPLES

The present invention will hereinafter be described more specifically bythe following Preparation Examples, Examples and Comparative Examples.All designations of part or parts and % as will be used in the followingexamples mean part or parts by weight and % by weight unless expresslynoted.

Various physical properties were determined in accordance with thefollowing respective methods:

(1) Glass Transition Temperature (Tg):

Tg of a polymer sample was measured by a differential scanningcalorimeter (DSC) in accordance with JIS K-7121. A value found from adisplacement point on a high-temperature side was regarded as Tg of thepolymer.

(2) Molecular Weight:

The molecular weight of a polymer sample was determined as a weightaverage molecular weight (Mw) in terms of polystyrene as measured by GPCusing toluene as a solvent. With respect to block copolymers, GPCmeasurement was conducted by using tetrahydrofuran (THF) as a solvent.

(3) Molecular Weight Distribution:

The molecular weight distribution of a polymer sample was determined byfinding a weight average molecular weight (Mw) and a number averagemolecular weight (Mn) in terms of polystyrene as measured by GPC usingtoluene as a solvent and calculating a ratio (Mw/Mn) of Mw to Mn. Withrespect to block copolymers, however, GPC measurement was conducted byusing tetrahydrofuran (THF) as a solvent.

(4) Rate of Hydrogenation:

Rates of hydrogenation in the aromatic rings and main chain in a polymersample were calculated by measuring ¹H-NMR.

(5) Molecular Weight of Hindered Amine Light-resistance Stabilizer:

The number average molecular weight of each hindered amine typelight-resistance stabilizer was determined by GPC using THF as asolvent.

(6) Light Transmittance:

The light transmittance (%) of each molded article was measured at aportion having an optical path length of 250 mm in a light guide plateby means of a spectrophotometer (U-30, manufactured by NipponBunko-sha).

(6) Light Resistance:

With respect to the evaluation of light resistance, a back light unitassembled with a light guide plate in accordance with a method describedbelow was continuously lighted for 1,500 hours, and a yellow index (ΔYI)of a long optical path (optical path length: 250 mm) of the light guideplate used was then measured by means of a long optical pathcolor-difference meter (ASA-300A, manufactured by Nippon Denshoku KogyoK. K.) to evaluate it as the degree of coloring.

(8) Evaluation of Gas Generation:

With respect to the generation of gases, a back light unit assembledwith a light guide plate in accordance with the method described belowwas continuously lighted for 1,500 hours, and whether a lamp reflectorcovering a cold cathode-ray tube was clouded or not was then visuallyobserved, thereby evaluating it in accordance with the followingstandard:

-   -   ⊚: No clouding was observed;    -   ∘: Clouding was somewhat observed at end portions of the        reflector, but the luminance of the light guide plate was not        affected to cause no problem on practical use;    -   Δ: The luminance of the light guide plate was slightly lowered        at its end portions because end portions of the reflector was        slightly clouded;    -   X: The whole reflector was clouded, and the luminance of the        whole reflector was lowered.        (9) Processing Ability:

With respect to the processing ability (processing stability), a ratio(A/B×100) of an amount (A) of HALS added to a vinyl alicyclichydrocarbon polymer upon twin-screw kneading, which will be describedsubsequently, to an amount (B) of HALS actually contained in the vinylalicyclic hydrocarbon polymer was determined as a retention rate toevaluate it.

(10) Flexural Strength:

A polymer sample was injection-molded to prepare a specimen having alength of 127 mm, a width of 12.7 mm and a thickness of 3 mm. Thisspecimen was used to measure the flexural strength of the specimen bymeans of a Strograph (V10-B, manufactured by Toyo Seiki Seisaku-sho Co.,Ltd.) in accordance with ASTM D-790, thereby evaluating it in accordancewith the following standard:

-   -   ⊚: A yielding point or break strength was 500 kgf/cm² or higher;    -   ∘: Break strength was not lower than 400 kgf/cm², but lower than        500 kgf/cm²;    -   X: Break strength was lower than 400 kgf/cm².        (11) Birefringence:

A copolymer sample was injection-molded to form an optical disksubstrate having a diameter of 85 mm. A birefringence value of thisoptical disk substrate at a position within a radius of 25 mm of thecenter was measured by means of a polarization microscope (manufacturedby NIKON CORP.; 546 nm Senarmont compensator) to evaluate it inaccordance with the following standard:

-   -   ⊚: 5 nm or less;    -   ∘: More than 5 nm, but not more than 10 nm;    -   X: More than 10 nm.

Preparation Example 1 Preparation of Hydrogenated Product of VinylAromatic Polymer

After a stainless steel-made reactor equipped with a stirrer was fullydried and purged with nitrogen, 960 parts of dehydrated cyclohexane, 240parts of a styrene monomer and 3.81 parts of dibutyl ether were chargedtherein. While stirring the contents of the reactor at 40° C., 0.65parts of a 15% hexane solution of n-butyllithium were added thereto toinitiate polymerization. After conducting the polymerization for 3 hoursat 40° C., 1.26 parts of isopropyl alcohol were added to stop thereaction. Mw of a vinyl aromatic polymer (polystyrene) thus obtained was180,000, and Mw/Mn was 1.04.

Then, 1200 parts of the solution containing the vinyl aromatic polymerwere transferred to a pressure reaction vessel equipped with a stirrer.To this reaction vessel, were added 24 parts of nickel-diatomaceousearth (N113, product of Nikki Chemical Co., Ltd.; amount of nickelcarried: 40%), and the mixture was stirred. The interior of the reactionvessel was purged with hydrogen gas, and hydrogen was supplied at 150°C. with stirring to conduct a hydrogenation reaction for 6 hours whileretaining the pressure to 70 kg/cm². After completion of thehydrogenation reaction, the reaction solution was filtered to remove thecatalyst. After removing the catalyst, 1,200 parts of cyclohexane wereadded to dilute the solution. This diluted solution was further filteredthrough a filter having a pore size of 1 μm under environment of acleanliness class of 1000 to remove foreign matter. The resultantfiltrate was poured into 9,000 parts of isopropanol filtered through afilter having an average pore size of 1 μm under environment of acleanliness class of 1000 to deposit a hydrogenated product of the vinylaromatic polymer. After the hydrogenated product was separated byfiltration, it was dried at 100° C. for 48 hours by a vacuum dryer tocollect the hydrogenated product of the vinyl aromatic polymer. Thephysical properties of the thus-obtained hydrogenated product were asfollows:

Tg=149° C.; Mw=153,000; and Mw/Mn=1.09.

Preparation Example 2 Preparation of Block Copolymer (BL₁)

A stainless steel-made reactor fully dried, purged with nitrogen andequipped with a stirrer-was charged with 320 parts of dehydratedcyclohexane, 28 parts of a styrene monomer and 0.40 parts of dibutylether. While stirring the contents of the reactor at 60° C., 0.30 partsof an n-butyllithium solution (15% hexane solution) were added theretoto initiate polymerization. After conducting the polymerization reactionfor 1 hour, 24 parts of a monomer mixture composed of 16 parts of astyrene monomer and 8 parts of an isoprene monomer were added to conductthe polymerization reaction for additional 1 hour. Thereafter, 28 partsof a styrene monomer were further added to continue the polymerizationreaction for 1 hour. To the reaction solution, were then added 0.2 partsof isopropyl alcohol to stop the reaction.

When the weight average molecular weight (Mw) and molecular weightdistribution (Mw/Mn) of the thus-obtained block copolymer were measured.As a result, Mw was 122,000, and Mw/Mn was 1.06.

Then, 400 parts of the polymerization reaction solution were transferredto a pressure reaction vessel equipped with a stirrer. To this reactionvessel, were added 10 parts of a nickel catalyst carried onsilica-alumina (E22U, product of Nikki Chemical Co., Ltd.; amount ofnickel carried: 60%), and the mixture was stirred. The interior of thereaction vessel was purged with hydrogen gas, and hydrogen was suppliedwhile stirring the solution to conduct a hydrogenation reaction for 8hours at a temperature of 160° C. and a pressure of 4.5 MPa.

After completion of the hydrogenation reaction, the reaction solutionwas filtered to remove the hydrogenation catalyst. After removing thecatalyst, 800 parts of cyclohexane were added to dilute the solution.This diluted solution was poured into 3,500 parts of isopropanol(filtered through a filter having an average pore size of 1 μm underenvironment of a cleanliness class of 1000) to deposit a blockcopolymer. The copolymer was separated and collected by filtration anddried at 80° C. for 48 hours under reduced pressure.

The thus-obtained block copolymer (BL₁) was a ternary block copolymercomposed of a block (hereinafter abbreviated as “St”) containingrepeating units derived from styrene, a block (hereinafter abbreviatedas “St/Ip”) containing repeating units derived from styrene and isopreneand a block (St) containing repeating units derived from styrene.

A molar ratio among the respective blocks in this block copolymer[St-(St/Ip)-St copolymer] was St:(St/Ip):St=33:34 (St:Ip=19:15):33. Thephysical properties of the block copolymer were as follows:

Mw=91,200; Mw/Mn=1.12; hydrogenation rate of the main chain and aromaticring=99.9%; Tg=125.5° C.; flexural strength=500 kgf/cm² or higher (⊚);and birefringence value=5 nm or less (⊚).

Preparation Example 3 Preparation of Block Copolymer (BL₂)

The same stainless steel-made reactor as that used in PreparationExample 2 was charged with 320 parts of dehydrated cyclohexane, 56 partsof a styrene monomer and 0.40 parts of dibutyl ether. While stirring thecontents of the reactor at 60° C., 0.30 parts of an n-butyllithiumsolution (15% hexane solution) were added thereto to initiatepolymerization. After conducting the polymerization reaction for 1 hour,24 parts of a monomer mixture composed of 16 parts of a styrene monomerand 8 parts of an isoprene monomer were added to conduct thepolymerization reaction for additional 1 hour. To the reaction solution,were added 0.2 parts of isopropyl alcohol to stop the reaction. When theweight average molecular weight (Mw) and molecular weight distribution(Mw/Mn) of the thus-obtained block copolymer were measured. As a result,Mw was 131,000, and Mw/Mn was 1.06.

A hydrogenation reaction was then conducted in the same manner asPreparation Example 2.

The thus-obtained block copolymer (BL₂) was a binary block copolymercomposed of St and St/Ip. A molar ratio among the respective blocks wasSt:(St/Ip)=66:34 (St:Ip=19:15). The physical properties of the blockcopolymer were as follows:

Mw=92,300; Mw/Mn=1.11; hydrogenation rate=99.9%; Tg=127.1° C.; flexuralstrength=500 kgf/cm² or higher (⊚); and birefringence value=5 nm or less(⊚).

Preparation Example 4 Preparation of Block Copolymer (BL₃)

The same stainless steel-made reactor as that used in PreparationExample 2 was charged with 320 parts of dehydrated cyclohexane, 3.2parts of a styrene monomer and 0.40 parts of dibutyl ether. Whilestirring the contents of the reactor at 60° C., 0.30 parts of ann-butyllithium solution (15% hexane solution) were added thereto toinitiate polymerization. After conducting the polymerization reactionfor 2 hours, 76.8 parts of a monomer mixture composed of 65.6 parts of astyrene monomer and 11.2 parts of an isoprene monomer were added toconduct the reaction for additional 1 hour. To the reaction solution,were added 0.2 parts of isopropyl alcohol to stop the reaction. When theweight average molecular weight (Mw) and molecular weight distribution(Mw/Mn) of the thus-obtained block copolymer were measured. As a result,Mw was 128,000, and Mw/Mn was 1.07.

A hydrogenation reaction was then conducted in the same manner asPreparation Example 2. The thus-obtained block copolymer (BL₃) was abinary block copolymer composed of St and St/Ip. A molar ratio among therespective blocks was St:(St/Ip)=4:96 (St:Ip=76.8:19.2). The physicalproperties of the block copolymer were as follows:

Mw=92,300; Mw/Mn=1.12; hydrogenation rate=99.9%; Tg=126.5° C.; flexuralstrength=not lower than 400 kgf/cm² but lower than 500 kgf/cm² (∘); andbirefringence value=more than 5 nm but not more than 10 nm (∘).

Example 1

To 100 parts of the vinyl aromatic polymer prepared in PreparationExample 1 were added 0.1 parts of a soft polymer (Toughtec H1052,product of Asahi Chemical Industry Co., Ltd.) and 0.1 parts of anantioxidant (Irganox 1010; product of CIBA-GEIGY AG), and 0.2 parts of apolycondensate [HALS (H₁); Mn=3000] of dibutylamine, 1,3,5-triazine,N,N′-bis(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexamethylenediamine andN-(2,2,6,6-tetramethyl-4-piperidyl)butylamine were further added as HALSto knead these components by means of a twin-screw kneader (TEM-35B,manufactured by Toshiba Machine Co., Ltd.; screw diameter=37 mm, L/D=32,screw speed=150 rpm, resin temperature=240° C., feed rate=20 kg/hr). Thekneaded mixture was extruded into a strand. This strand was cooled withwater and cut by a pelletizer to provide pellets.

The content of HALS (H₁) in the pellets was measured by gaschromatography and was found to be 0.2% based on the whole weight of theresin composition, and so a ratio (retention rate) of an actual contentof HALS to an amount of HALS added was substantially 100%.

After the pellets thus obtained were dried at 70° C. for 2 hours bymeans of an air-circulated hot-air dryer to remove water, a light guideplate 10.4 inches in size was molded by injection molding using aninjection molding machine (Lot No. IS450, manufactured by ToshibaMachine Co., Ltd.) of a side gate mold system having a hot runner. Themolding was conducted under conditions of a mold temperature of 80° C.and a cylinder temperature of 280° C.

The thus-obtained light guide plate was such a wedge form that athickness of a thick wall portion on the side of a plane of incidence is2.5 mm, a thickness of a thin wall portion on the opposite side is 1.5mm, a length from the thick wall portion to the thin wall portion is 190mm, a length along an axial direction of a linear light source is 250mm, and the thickness becomes gradually thin as it leaves from the thickwall portion to the thin wall portion (in a direction substantiallyperpendicular to the axis of the linear light source). The lighttransmittance of the light guide plate was measured at the portion 250mm in length along the axial direction and found to be 85%.

A white ink pattern for light reflection was formed on one side of thewidest surface of the light guide plate. The end surface of the portion2.5 mm in thickness of the light guide plate was used as a plane ofincidence, a cold cathode-ray tube and a lamp reflector were provided onsaid end surface side, and a light reflection sheet was provided on theend surface to fabricate a back light unit.

After the cold cathode-ray tube was continuously lighted for 1,500hours, the degree of coloring (yellow index) of the light guide platewas determined, and the clouded state of the lamp reflector was visuallyobserved. The results are shown in Table 1.

Example 2

A resin composition was prepared in the same manner as in Example 1except that a polymer [HALS (H₂); Mn=3,550] of dimethyl succinate and4-hydroxy-2,2,6,6-tetramethyl-1-piperidine ethanol was used as HALS, andthe resin composition was used to fabricate a light guide plate andevaluate it. The results are shown in Table 1.

Example 3

A resin composition was prepared in the same manner as in Example 1except thatpoly[{(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazin-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}][HALS (H₃); Mn=2,550] was used as HALS, and the resin composition wasused to fabricate a light guide plate and evaluate it. The results areshown in Table 1.

Comparative Example 1

A resin composition was prepared in the same manner as in Example 1except that bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate [HALS (H₄);Mn=481] was used as HALS, and the resin composition was used tofabricate a light guide plate and evaluate it. The results are shown inTable 1.

Comparative Example 2

A resin composition was prepared in the same manner as in Example 1except thatbis(2,2,6,6-pentamethyl-4-piperidyl){[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl}butylmalonate [HALS (H₅); Mn=685] was used as HALS, and the resin compositionwas used to fabricate a light guide plate and evaluate it. The resultsare shown in Table 1.

Comparative Example 3

A resin composition was prepared in the same manner as in Example 1except that a mixture [HALS (H₆); Mn=509] ofbis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate andmethyl-1,2,2,6,6-pentamethyl-piperidyl sebacate was used as HALS, andthe resin composition was used to fabricate a light guide plate andevaluate it. The results are shown in Table 1.

Comparative Example 4

A resin composition was prepared in the same manner as in Example 1except that the amount of HALS (H₁) added was changed from 0.2 parts byweight to 25 parts by weight, and the resin composition was used tofabricate a light guide plate and evaluate it. The results are shown inTable 1.

TABLE 1 Processing Light Generation Resin composition (parts) abilityresistance of gas HALS Retention ΔYI after Clouding Hydrogenated SoftAnti- Molecular Amount rate of Light continuous of polystyrene polymeroxidant Kind weight added HALS transmittance Lighting reflector Ex. 1100 0.1 0.1 H₁ 3000 0.2 100 85 15.8 ⊚ Ex. 2 100 0.1 0.1 H₂ 3550 0.2 10082 16.4 ⊚ Ex. 3 100 0.1 0.1 H₃ 2550 0.2 95 87 16.1 ◯ Comp. 100 0.1 0.1H₄ 481 0.2 70 88 21.5 X Ex. 1 Comp. 100 0.1 0.1 H₅ 685 0.2 75 87 19.2 ΔEx. 2 Comp. 100 0.1 0.1 H₆ 509 0.2 70 89 20.7 X Ex. 3 Comp. 100 0.1 0.1H₁ 3000 25 90 79 18.5 Δ Ex. 4

Example 4

A resin composition was prepared in the same manner as in Example 1except that 0.1 parts of 2-(2′-hydroxy-5′-methylphenyl)benzotriazole[ultraviolet absorbent (U₁)] was further added, and the resincomposition was used to fabricate a light guide plate and evaluate it.The results are shown in Table 2.

Example 5

A resin composition was prepared in the same manner as in Example 1except that 0.1 parts of2-(2H-benzo-triazol-2-yl)-4-methyl-6-(3,4,5,6-tetrahydrophthalimidyl-methyl)-phenol[ultraviolet absorbent (U₂)] was further added, and the resincomposition was used to fabricate a light guide plate and evaluate it.The results are shown in Table 2.

Example 6

A resin composition was prepared in the same manner as in Example 1except that 0.1 parts of2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol[ultraviolet absorbent (U₃)] was further added, and the resincomposition was used to fabricate a light guide plate and evaluate it.The results are shown in Table 2.

TABLE 2 Resin composition (parts) Processing Light Generation Hydro-HALS UV absorbent ability resistance of gas genated Mole- RetentionLight ΔYI after Clouding poly- Soft Anti- cular Amount Amount rate oftransmit- continuous of styrene polymer oxidant Kind weight added Kindadded HALS tance lighting reflector Ex. 4 100 0.1 0.1 H₁ 3000 0.2 U₁ 0.1100 85 15.2 ⊚ Ex. 5 100 0.1 0.1 H₁ 3000 0.2 U₂ 0.1 100 85 15.4 ⊚ Ex. 6100 0.1 0.1 H₁ 3000 0.2 U₃ 0.1 100 84 15.5 ⊚

Example 7

A resin composition was prepared in the same manner as in Example 1except that the block copolymer (BL₁) prepared in Preparation Example 2was used in place of the vinyl aromatic polymer prepared in PreparationExample 1, and the resin composition was used to fabricate a light guideplate and evaluate it. The results are shown in Table 3.

Example 8

A resin composition was prepared in the same manner as in Example 1except that the block copolymer (BL₂) prepared in Preparation Example 3was used in place of the vinyl aromatic polymer prepared in PreparationExample 1, and the resin composition was used to fabricate a light guideplate and evaluate it. The results are shown in Table 3.

Example 9

A resin composition was prepared in the same manner as in Example 1except that the block copolymer (BL₃) prepared in Preparation Example 4was used in place of the vinyl aromatic polymer prepared in PreparationExample 1, and the resin composition was used to fabricate a light guideplate and evaluate it. The results are shown in Table 3.

TABLE 3 Resin composition (parts) Processing Light Generation Blockability resistance of gas copolymer HALS Retention ΔYI after CloudingAmount Soft Anti- molecular Amount rate of Light continuous of Kindadded polymer oxident Kind weight added HALS transmittance lightingreflector Ex. 7 BL₁ 100 0.1 0.1 H₁ 3000 0.2 100 85 15.6 ⊚ Ex. 8 BL₂ 1000.1 0.1 H₁ 3000 0.2 100 85 15.5 ⊚ Ex. 9 BL₃ 100 0.1 0.1 H₁ 3000 0.2 10082 15.5 ⊚

Example 10

A resin composition was prepared in the same manner as in Example 7except that 0.1 parts of 2-(2′-hydroxy-5′-methylphenyl)benzotriazole[ultraviolet absorbent (U₁)] was further added, and the resincomposition was used to fabricate a light guide plate and evaluate it.The results are shown in Table 4.

Example 11

A resin composition was prepared in the same manner as in Example 7except that 0.1 parts of2-(2H-benzo-triazol-2-yl)-4-methyl-6-(3,4,5,6-tetrahydrophthalimidyl-methyl)-phenol[ultraviolet absorbent (U₂)] was further added, and the resincomposition was used to fabricate a light guide plate and evaluate it.The results are shown in Table 4.

Example 12

A resin composition was prepared in the same manner as in Example 7except that 0.1 parts of2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol[ultraviolet absorbent (U₃)] was further added, and the resincomposition was used to fabricate a light guide plate and evaluate it.The results are shown in Table 4.

TABLE 4 Resin composition (parts) Processing Light Generation Block HALSability resistance of gas copolymer Mole- UV absorbent retention LightΔYI after Clouding Amount Soft Anti- cular Amount Amount rate oftransmit- continuous of Kind added polymer oxidant Kind weight addedKind added HALS tance lighting reflector Ex. 10 BL₁ 100 0.1 0.1 H₁ 30000.2 U₁ 0.1 100 85 15.1 ⊚ Ex. 11 BL₁ 100 0.1 0.1 H₁ 3000 0.2 U₂ 0.1 10085 15.3 ⊚ Ex. 12 BL₁ 100 0.1 0.1 H₁ 3000 0.2 U₃ 0.1 100 84 15.3 ⊚

INDUSTRIAL APPLICABILITY

According to the present invention, there are provided resincompositions which are excellent in transparency, heat resistance andprocessing stability, are not colored even when they are used for a longperiod of time under lighting and do not generate gases. According tothe present invention, there are provided light guide plates obtained byforming or molding such a resin composition, having excellenttransparency, heat resistance and light resistance and undergoing nogeneration of gases. The light guide plates according to the presentinvention are useful in the technical field of liquid crystal displaydevices as light guide plates for plane emission illuminators.

1. A resin composition comprising a vinyl alicyclic hydrocarbon polymerwhich is a homopolymer or copolymer containing, in its main chain,repeating units [1] of a structure represented by the following formula(1):

wherein X is an alicyclic hydrocarbon group, and R¹ to R³ are,independently of one another, a hydrogen atom, linear hydrocarbon group,halogen atom, alkoxy group, hydroxyl group, ester group, cyano group,amide group, imide group, silyl group, or linear hydrocarbon groupsubstituted by a polar group, and the content of the repeating units [1]in the vinyl alicyclic hydrocarbon polymer is at least 50% by weight,and which has a saturated alicyclic hydrocarbon group containingcarbon-carbon unsaturated bonds of at most 20% based on the wholecarbon-carbon bond, and 0.01 to 20 parts by weight, per 100 parts byweight of the vinyl alicyclic hydrocarbon polymer, of a hindered aminelight-resistance stabilizer having a plurality of piperidine rings withsubstituent group(s) bonded to both carbon atoms adjacent to thenitrogen atom and having a number average molecular weight (Mn) of 1,000to 10,000 as determined by gel permeation chromatography.
 2. The resincomposition according to claim 1, wherein the hindered aminelight-resistance stabilizer has a melting point of at least 20° C. 3.The resin composition according to claim 1, wherein the hindered aminelight-resistance stabilizer is a high molecular weight hindered aminetype light-resistance stabilizer with a plurality of piperidine ringsbonded through a triazine skeleton.
 4. The resin composition accordingto claim 1, wherein the hindered amine light-resistance stabilizer is ahigh molecular weight hindered amine type light-resistance stabilizerwith a plurality of piperidine rings bonded through an ester linkage. 5.The resin composition according to claim 1, which further comprises anultraviolet absorbent.
 6. The resin composition according to claim 5,wherein the ultraviolet absorbent is at least one compound selected fromthe group consisting of 2-(2′-hydroxy-5′-methylphenyl)benzotriazole,2-(2H-benzotriazol-2-yl)-4-methyl-6-(3,4,5,6-tetrahydrophthalimidylmethyl)phenoland 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)-phenol. 7.The resin composition according to claim 1, which further comprises atleast one compounding additive selected from the group consisting of (i)a soft polymer, (ii) an alcoholic compound and (iii) an organic orinorganic filler.
 8. The resin composition according to claim 1, whereinthe vinyl alicyclic hydrocarbon polymer is a hydrogenated product of apolymer of a vinyl aromatic compound.
 9. The resin composition accordingto claim 1, wherein the vinyl alicyclic hydrocarbon polymer is ahydrogenated product of a copolymer of a vinyl aromatic compound and amonomer copolymerizable with the vinyl aromatic compound.
 10. The resincomposition according to claim 1, wherein the vinyl alicyclichydrocarbon polymer is a block copolymer containing a polymer block [A]containing repeating units [3] represented by the following formula (3):

wherein R³ is a hydrogen atom or an alkyl group having 1 to 20 carbonatoms, and R⁴ to R¹⁴ are, independently of one another, a hydrogen atom,an alkyl group having 1 to 20 carbon atoms, a hydroxyl group, an alkoxygroup having 1 to 20 carbon atoms or a halogen atom, and a polymer block[B] containing repeating units [5] represented by the following formula(5):

wherein R¹⁵ is a hydrogen atom or an alkyl group having 1 to 20 carbonatoms, and/or repeating units [6] represented by the following formula(6):

wherein R¹⁶ to R¹⁷ are, independently of each other, a hydrogen atom oran alkyl group having 1 to 20 carbon atoms, and wherein the totalcontent of the repeating units [3] in the block copolymer is at least50% by weight.
 11. The resin composition according to claim 10, whereinthe block copolymer further contains the repeating units [3] in thepolymer block [B], and a mole fraction a (mol %) of the repeating unitsin the polymer block and a mole fraction b (mol %) of the repeatingunits [3] in the polymer block [B] satisfy the relationship of a>b. 12.The resin composition according to claim 10, wherein supposing that thenumber of moles of the whole repeating unit [A] forming the block ism_(a), and the number of moles of the whole repeating unit forming theblock [B] is m_(b), a ratio (m_(a):m_(b)) thereof is 4:96 to 96:4.
 13. Alight guide plate obtained by forming or molding the resin compositionaccording to any one of claims 1 to 12.